True maybe it was rolled over when they changed the location of the number in 52 i beleive? or else they left a digit out on yours :? my bad sorry I overlooked that :?
It is probably a pre-48. There was a fire in the Schwinn factory on August 18, 1948 and all the records before that were lost. Typically folks look to the date cast into the crank to date the pre-48 bikes. If you don't have the original crank you can check some of the other parts. Schwinn was good about dating their parts. If you don't have any of the parts several of the members have compiled a list that may help.